Glow discharge tube



Dec. 11, 1934. M. PONTE 1,983,638

GLOW DISCHARGE TUBE Filed May 20, 1955 INVENTOR MVW ATTORNEY PatentedDec. 11,

The present invention is concerned with gasin which the variations ineous discharge tubes PATENT OFFICE GLOW DISCHARGE TUBE Maurice Ponte,Paris,

pagnie 'Generale De France, 'assignor to Com- Telegraphie Sans Fil, a

corporation of France Application May 20, 1933, Serial 'No. 672,033

In France June 7,

10 Claims.

length of a luminous column as a function of the current flowing through5 purpose of insuring v nous tubes such as for modulation (modulationmeters the tube are used for the arious applications of lumirecording,indicators of etc.

Especially in this latterinstance it is often desirable to be abletoutilize tubes of large size I designed to respond to Assurance ofsufilciently great the following conditions:

brightness without'the tube being traversed by large currents,

these being conditions imposed by applications and uses of thesetubeswhere they are called upon to operate with tubes or copiousdisintegration o avoided therein generators-of low output,

r spattering having to be so as to prevent undue blacking of the bulb.At the same-time, the law of variation intensity. should further sible.

luminous discharge de comparative character utilizing the cathode shownof the length of the column as a function of the more be as linear asposwhich forms part 1 shows one form of a vice. Fig. 2' represents istic1 curves of "devices in Figs. 1 and 3. Fig.

3 showsa cathode construction according to the present invention. Fig.

. teristic curve o 4-represents the characf a device utilizing thecathode shown in Fig. 3, but with the cathode'wire consisting ofnichrome wire,

and Fig. 5 shows the complete luminous discharge device according to theinvention. I

As has been known for a long time, tubes of this kind consist of acathode of tubular or filamentary shapemounted in the axis of atubularbulb which do mprises and contains an anode.

The variations observed are those of the length of the negative glow asintensity.

Fig. 1 shows a unction of the current tube constructed in this mannerwhere 1 denotes the anode and 2 the cathode extending alongside whichwill be observed the luminous sheath or cloak, the-assembly beingmounted inside of a suitable pressure. uction of tubes of great a bulb 3which has conprinciple is attended with following diificultie'sz In thelength of the cathode rod grows sufiicient diameter so as to the currentrequired for the tube grows so that .be fed from a low-power generatorsuch as a small multi-electrodetube.. Since at the same time the powerdissipated in-v side the tube becomes relatively large (say, 10 wattsand over) the cathode becomes subject to fast pulverization ordistintegration, with the result that the tube is renderedunserviceable' even after a few hours of use. Finally, thecharacteristic curve of the tube which represents the variations inlength of the column as a function of the current flowing through thetube pre-' 10 sents a state of saturation that is extremely markedwhenever the column reaches a length near its maximum. Curve 2a,by wayof example,

represents the characteristic graph of a tube whose cathode, has a gasis at a pressure of 2.5 mm. (diameter of cathode rod being 3.5 mm). The.abscissa in terms of milliamperes indicate the values of the currentflowing, hrough the tube, while the ordinates give the length of thenegative glow in 20 millimeters. After a certain length, the negativecolumn is found to grow but very little as the current increases, anaction that is often troublesome because the useful length of the tubeis reduced. vTubes of reduced dimensions more: over present similar.saturation phenomena. It is impossible to remedy these difiiculties byreducing the pressure prevailing inside the tube seeing that the darkspace would grow at the same time, and the tube would become impaired inbrightness orluminosity.

The present invention obviates these difiiculties as hereinbeforedescribed in that it discloses ways and means of constructing tubes ofgreat length, of adequate brightness, low consumption and linearcharacteristic, this latter advantage being realizable also in tubesofsmaller dimensions.

With this end in View, a first object of the invention consists in usingas the cathode an insu- 0 lating tube or rod or stick having the desireddiameter upon which is applied a conductor whose effective surface orarea is only a fraction of that of the insulating tube. A preferablemode of carrying this latter idea into practice is to form the conductorof a helix made up of a fine conductor wire wrapped around the rod at apitch to be chosen according to practical requirements. Fig. 3represents a cathode thus constituted, 1 being the insulating rod, and 2the conductor wire, the end portion 3 being shown in section. Comparedwith a tube containing a solid cathode of similar dimensions, thisscheme insures reduced consumption, at the same gas pressure. In Fig. 2the curves 2a and 21) represent the comparative charlength of 320 mm.and whose 15* acteristics of two similar tubes operated under similarconditions except for the cathode construction, the tube Whosecharacteristic is represented'by curve 2b being provided with theimproved cathode shown in Fig; 3, while the tube whose characteristic isrepresented by curve 264 is provided with a cathode of the type shown inFig. 1, which does not have a helical conductor wound about the cathoderod. '7

It will be noted that the characteristic of this tube, while improvedfrom the viewpoint of energy consumption always involves the property ofsaturation. According to the-second object and part of this invention,the shape or trend of the characteristic can be modified and renderedlinear by using for the conductor to be wrapped about the insulator rodan element sufficiently resistant in order that the current of the tubemay set up a potential difference along the cathode. Indeed, it'

is evident that the saturation phenomenon will be less pronounced if,instead of leaving or allowing the surface of the cathode to becomeequipotential in nature, a fall of potential is created thereon whichgrows in proportion as the cathode glow approaches the end of thecathode located opposite to or facing the anode. The most convenient wayto that end consists in employing for the wire wrapped round theinsulator rod a fine and resistant wire. This method is rather elastic,as it were, for, in order to modify the characteristic, it is possibleto act on or change the diameter of the wire, its nature, and thewinding pitch. Indeed, these factors may be chosen in a way so that thecharcteristic will turn out linear and assume a shape such as indicatedfor example in Fig. 4'. This graph has been plotted for a tube similarto that for which the characteristics shown by curve 2b in Fig. 2 hasbeen plotted, but whose cathode wire consists of a nichrome wire of33/1000 wound with a pitch of 0.3 mm. upon a glass rod of 3.5 mm.diameter. itbeing understood that these figures are merely given by wayof example. The resistance of the tubes obviously will be raised, butthis is no inconvenience because they can be excited by tubes of highinternal resistance, such as those which are known in the art as screengrid tubes.

It will be noted that in the arrangement of this invention the length ofthe column is directly controlled or determined by the modulatedcurrent, and that it is the variations of the current of the tube whichserve to create the auxiliary differences of potential that are used toimprove its characteristic. Hence, the basic principle of the inventiondiifers from that of certain tubes used in recording work wherein use ismade of an electrode on which is created a potential difference by meansof an auxiliary battery with a modulation potential being superposedthereon. The two electrodes (or the single equivalent electrode) are inthat case parallel and the length of the discharge is determined by thepoint where the voltage falls below the ignition or flash potential. Thesituation is wholly different in the present case and tube where theproperties of the negative glows are used and where, no matter at whatpoint the tube may be working, the voltage will never fall below theflash potential.

Fig. 5 finally represents a tube constituted in accordance with thepresent invention as an example of an industrial product without anylimitations being imposed as regards its character. 1' denotes aninsulating tube made from glass which supports the resistor wire 2 whichrepresents the cathode conductor and which is brought out at 4'. Theanode 3 serves also to support the rod 1, the assembly being mountedinside a bulb 5' in the interior of which is the filling gas atmosphere.6' is the anode lead-in conductor. The dimensions of the elements of thetube, for instance, may be the same as hereinbefore suggested, thoughitwill be understood that there is no objection to use, for instance, adifferent pitch so as to alter the shape of or the law governing thenegative glow in the case of certain practical applications.

What is claimed is:

1. A discharge device comprising a gas filled envelope and a pair ofcoaxially disposed electrodes between which a discharge may be passedlocated therein, one of said electrodes comprising a support extendinglinearly in said envelope and a resistance wire wound about saidelectrode. *2. A discharge device comprising a long tubular gas filledvessel, an anode. and a cathode, the latter comprising along insulatingrod extending axially of said tubular vessel, and a high resistance wirehelically wound about said insulating rod for a substantial distancethereof, the anode being coaxially disposed with respectto the cathodeinsulating rod.

3. A discharge device comprising a'tubular gas filled vessel, an anodeat one end of said vessel, a substantially lengthy insulating rodextending axially of said tubular vesseland coaxially with respectQtothe anode, and a nichrome wire helically wound about said insulating rodfor a substantial distance thereof.

4. A glow discharge device comprising a tubular gas filled vessel, asubstantially lengthy glass rod extending axially bf said tubularvessel, a disc-shaped anode located at one end of said vessel and havinga central opening through which one end of said glass rod is insertedfor supporting the same, and a fine resistance wire helically woundabout said glass rod for a substantial distance thereof.

5. A glow discharge device comprising a tubular gas filled vessel, asubstantially lengthy glass rod extending axially of said tubularvessel, a disc-shaped anode located at one end of said vessel and havinga central opening through which one end of said glass rod is insertedfor supporting the same, and a fine nichrome wire helically wound aboutsaid glass rod for a substantial distance thereof.

6. A luminous discharge device comprising a gas filled vessel, ahelically wound cathode and an anode coaxially aligned within the vesseland between which a discharge may be passed, and means for creating apotential difference along the cathode comprising a source of potentialconnected between the anode and one end only of the cathode.

'7. A current indicating device comprising a gas filled tubular vessel,a pair of coaxially aligned electrodes therein between which a dischargemay be passed, one of said electrodes comprising a substantially lengthyinsulating rod and a fine wire resistance coil wrapped about the surfaceof said rod, and means for applying a suitable potential between theanode and one extremity of said coil, the other extremity thereof beingopen, whereby a potential difference is created along the surface ofsaid rod of such value that length of the discharge is linearlyproportional to the current intensity through the device.

8. A current indicating device comprising a gas filled tubular vessel, apair of coaxially aligned electrodes therein between which a dischargemay be passed, one of said electrodes comprising being small as comparedwith the support sura substantially lengthy insulating rod, and meansface, and means for applying a potential differfor applying a suitablepotential between the ence to said electrodes. anode and one extremityof said wire, the other 10. A discharge device for indicating currentsextremity thereof being open, and a fine niohrome conducted therethroughby the length of a glow wire wrapped about the surface of said rodluminous column, comprising a gas-filled tubular whereby a potentialdifference is created along vessel, a pair of electrodes axially alignedtherethe surface of said rod of such value that length in, one of saidelectrodes comprising a substanof the discharge is linearly proportionalto the tially lengthy insulating support and a resistant currentintensity through the device. conductor disposed thereupon, the surfaceof the 1 9. A discharge device for indicating currents conductor beingsmall as compared with the supconducted therethrough by the length of aglow port surface, and the resistance of the former luminous column,comprising a gas-filled tubular being so selected that the dischargeluminous vessel, a pair of electrodes axially aligned therein, length isproportional to the discharge current, one of said electrodes comprisinga substantially and means for applying a potential difference to 15lengthy insulating support and a conductor dissaid electrodes. posedthereupon, the surface of the conductor MAURICE PONTE.

